Nowadays, with the rapid development of communication networks such as Internet and the like, information searches through the communication networks have been generalized. If a user attempts to access a desired search engine using an Internet access browser installed at his/her PC, he/she inputs a desired keyword in a search window. The input keyword is transferred to a search server of a search site (or portal site) via the communication networks. The search server including a search DB retaining a plurality of search list orders corresponding to the keywords transfers a search result list consisting of search list orders, as a result of the search request from the user, to the user's PC. The user can easily access a desired web site by clicking a search list order of the web site among the search result list displayed on a screen of his/her PC.
As the information search through the search site becomes greatly frequent in this way, search list order display methods for providing advertisements (for example, banner advertisements) associated with the keywords, which are inserted into a search result list screen or linked with the search list order, come into the spotlight day by day as new advertisement systems. In view of search site providers, these new advisement systems became a big profit source over paid contents services.
Further, as the frequency of exposure to network users and the number of inquiry by the users show a great difference depending on an occupation position of the search list order associated with a web site provided by the network information provider in a search result list, the occupation position of the search list order in the search result list has a significant influence on an advertisement effect of the web site. Accordingly, a “keyword selling” for connecting a search list order, which is disposed in a position within the search result list at which the frequency of exposure to network users and the number of inquiry by the users are high, with a web site of a particular network information provider has been generalized in search site businesses.
However, keyword selling systems conducted by conventional search sites adopt a first-come first-served selling system. This system is a system for setting start time of selling for a particular keyword in advance and determining a final purchaser on a first-come first-served basis among a plurality of purchase requests received after the start of the selling. However, this system has a big problem due to excessive purchase competition between many network information providers when they sell particularly favorite keywords (referred to as premium keywords in the art). In other words, there occurs a case where a selling system does not operate normally due to an overload imposed on a communication network as a plurality purchase requests rushes through the communication network in compliance with start time for selling, and, although a normal selling is achieved, there causes a problem in that a suspicion on selling fairness from network information providers who do not purchase their favorite keywords is raised. In addition, there is an inconvenience in that network information providers have to make much unnecessary efforts for first-come first-served purchase requests for their favorite keywords.
In view of the search sites, there is a difficulty in estimating selling prices of keywords in a highly competitive field.
There have been accordingly made efforts to sell keyword goods to network information providers at fair prices and offer a search result list reasonably by reflecting fair selling prices. Korean Patent Application No. 10-2001-7015234 discloses a method in which keywords are sold by an auction system and search list orders are aligned in a search result list according to the highest bid price by auction. The method disclosed in the above patent application adopts a system where network information providers pay in advance an amount of money corresponding to an expected number of clicks to select a search list order during a certain period of time and the amount of money is offset by the highest bit price by auction every time a click is made. However, since a position of a search list order is uniformly defined by one criterion of the highest bid price by auction even according to this selling system and the formation of search result list, there still exists a problem in that network information providers cannot select a position of a search list order or a variety of search list order display methods cannot be offered to them. In addition, in the above patent application, since the position of the search list order can be consecutively changed by reflecting an auction result in real time, there is a problem in that an advertisement effect originally intended by the network information providers may be reduced over time. In addition, owing to an inherent limitation to the auction system in determining keyword selling prices, there is an inevitable problem of unreasonable price decision due to an excessive competition.